An overall aim of the SCOR is to elucidate mechanisms of airway hyper- reactivity using, in part, animal models. A critical feature of the SCOR is to provide transgenic mice as appropriate models. The transgenic core will provide transgenic animals to the SCOR on either F2 or appropriate inbred mouse backgrounds. It will also provide a ~speed backcrossing~ service whereby DAN polymorphisms will be used to facilitate rapid backcrossing of any given transgene onto an appropriate inbred background. Finally, the core will develop regulated transgenes that permit the expression of given gene products in the airways to be controlled by exogenous manipulation at the will of the investigator.